Arup will draw up a cost analysis of the suitability of a London bid for the government-led consortium overseeing the bid. The report is expected to be complete by May.
The campaign to stage the games comes despite embarrassing setbacks over the Wembley national stadium project and the collapse of a World Athletics Championships bid.
Sports minister Richard Caborn is understood to be enthusiastic about the prospects of a London games.
Arup's appointment, made by the government, the Greater London Authority and the British Olympic Association, will be formally announced at the end of this month.
A spokesperson for GLA regeneration body the London Development Agency said the report would look for a location in London for the games. He added: "The analysis will examine the cost of bidding, the cost of hosting and the regeneration implications."
Stratford in east London remains the favoured site of London mayor Ken Livingstone. The mayor and the LDA are putting up half the money for the £400,000 report.
A previous study by property agent Insignia Richard Ellis identified several potential sites. In an independent report last year, Arup said Stratford could accommodate an 80,000-seat stadium.
Arup will look at the cost of bidding, hosting and regeneration
London Development Agency
A spokesperson for the Department for Culture, Media and Sport said the report would also examine the possibility of spreading the games around London. He said: "Looking at London as a whole, there aren't too many sites big enough to house a games. If there isn't a piece of land big enough we will have to look at housing the games across London." Proposals to turn the Millennium Dome into a 20,000-seat sports stadium will be considered.
Wembley has, in effect, been ruled out as a site for the main stadium because it is likely to have only a temporary athletics track. The DCMS spokesperson said: "If the International Olympic Committee states it wants the stadium to have a permanent athletics track then Wembley's design would rule it out."
Stadium designs will not be drawn up yet, but certain specifications will have to be decided. The DCMS spokesperson said: "If a bid is going to pass the scrutiny of the Treasury and colleagues across Whitehall then the report is going to have to be sufficiently rigorous. The decision to go ahead will be taken up to, and including, the prime minister."
The report is also expected to produce an environment impact assessment.
The IOC and the International Union of Architects are to hold a conference for potential bidders in Lausanne, Switzerland, in June.
As reported in Building last week, Wembley National Stadium Limited acted in response to criticisms of its corporate structure by independent adviser David James. The board is expected to be cut from 13 to eight.
Few of the board will remain, but Football Association chief executive Adam Crozier and WNSL chairman Sir Rodney Walker will stay.